Estimating PM 2.5 concentrations using MODIS and meteorological measurements for the San Francisco Bay Area

Ground-level fine particulate matter (PM2.5) is a major component of urban air pollution with links to adverse health effects and is regulated by the EPA to meet federal standards. Aerosol Optical Depth (AOD) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensors can be used as an indirect measurement of PM2.5 due to the attenuation of atmospheric transmission of light by aerosols. This method has the potential to greatly increase spatial coverage of PM measurements and provide cost effective information for air quality decision-makers; however, regional differences alter the relationship between AOD and PM2.5. A multivariate analysis is presented in this study to predict PM2.5 concentrations in the San Francisco Bay Area from MODIS AOD and meteorological variables from ground-stations and Rapid Update Cycle (RUC) reanalysis products. Twelve PM2.5 monitoring stations are used for model training over a one year period. PM2.5 distributions were fairly uniform throughout the region with R2 values between 0.06 and 0.28. PM2.5 was highest during the winter and at night when lower boundary layer heights and cold temperature inversions help to concentrate pollutants closer to the earth’s surface. The results of this study confirm previous studies that found low correlations between AOD and PM2.5 in the western U.S.